It is commonly known to carry out x-ray CT examinations of the heart with contrast agent present. In the case of these examinations, the individual coronary vessels visually stand out due to the presence of contrast agent, with dedicated visualization algorithms being used for better display of these vessels and showing in three dimensions only the vessels filled with contrast agent, without other artifacts. If such segmentation is carried out automatically for all vessels filled with contrast agent, the problem arises that the chambers of the heart, which are surrounded by the coronary vessels, are also segmented, as a result of which the smaller vessels fade into the background and thus their evaluation deteriorates. Although in principle it is possible to individually segment single vessels by manual inputs so that finally a multiplicity of single vessels are segmented without the chambers of the heart, such a method is however firstly very time consuming and secondly there is the risk of overlooking or incorrectly segmenting single vessels, that is to say overestimating or underestimating the vessel size due to the manual operation. A further problem is that such a view of individually displayed segmented vessels does not correspond to the view a cardiologist is used to from cardiac catheter examinations.